Business Segments (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure Business Segments Summary Of Companys Segment Results [Abstract]
Number of principal business operations		3
Extinguishment Of Debt [Line Items]
Net gains (losses) on extinguishment of debt	$ 6	$ 3	$ 49
Medium Term Notes [Member]
Extinguishment Of Debt [Line Items]
Retired medium-term notes		129
Net gains (losses) on extinguishment of debt		$ 4